Anemia is a common health problem in US older populations;and it increases the risk for disability, decline in physical performance, low muscle strength, and premature death in the elderly. A recent study from NHANES III reported the prevalence of anemia being larger than 10% in the US population over age 65, and the prevalence of anemia varied by ethnicity, suggesting significant health disparities in minorities, especially in the African American population. In this study, a large (N >160,000) multiethnic (non-Hispanic white, Hispanic, African American, Native American, Asian/Pacific Islander) cohort from the nationwide Women's Health Initiative (WHI) study will be used to investigate the relationships of aging with anemia epidemiology, pathology and prognosis. Specifically, we will 1) evaluate the frequency of and risk factors for anemia overall and according to race-ethnicity and co-morbidity;2) determine the association between anemia and risk of death over 10 years of follow-up in the WHI overall and by race-ethnicity;3) determine associations between anemia and changes in physical function over 9 years of follow-up in the WHI cohort overall and by race- ethnicity;4) examine associations of anemia with muscle loss (sarcopenia) among those with baseline and prospective measurements of body composition from dual-energy x-ray absorptiometry;and 5) study the association of anemia with bone loss and risk for osteoporotic fractures in older women. In addition, the frequency of anemia subtypes by morphologic categories and optimal cutoff points of hemoglobin concentrations for anemia in older women will be evaluated. This study will use archived observational and clinical trial data from 40 WHI clinical centers. Additional data entering for blood analysis from existing reports, and data merging (body composition measurements) will be conducted in the WHI DXA cohort from Arizona, Birmingham and Pittsburgh. Multivariate data analyses will be conducted for the specific aims. The WHI provides a unique and invaluable resource for answering the research questions proposed above, as the WHI is the only study in the nation that has prospective co-morbidities and body composition data as well as hemoglobin values in multiethnic groups of older women. This study has a great potential to provide new and critical evidence that is needed for preventing and managing anemia in older women from different health, age and ethnic backgrounds.